Hydraulically expansible rotary drill bits



July 17, 1956 A w. KAMMERER, JR 2,755,070

HYDRAULICALLY EXPANSIBLE ROTARY DRILL BITS July 17, 1956 A. w. KAMMERER,JR 2,755,070

-' HYDRAULICALLY EXPANSIBLE ROTARY DRILL BITS Filed Aug. 25, 1954 2sheets-sheet 2 i294. j?? e.

1N VEN TOR. QCHEQ W EAMMEeE/Q, Je.

United States Patent HYDRAULICALLY EXPANSIBLE ROTARY DRILL BITS ArcherW. Kammerer, Jr., Fullerton, Calif., assignor, by direct and mesneassignments, to Rotary @il Tool Conrpany, Huntington Park, Calif., acorporation of Caufornia Application August 25, 1954, Serial No. 452,184

19 Claims. (Cl. Z55-76) The present invention relates to rotary drillbits of the expansible type, capable of being lowered through wellcasing and of drilling or enlarging a bore hole below the casing to agreater diameter than the inside diameter of the casing.

An object of the present invention is to provide an expansible rotarydrill bit having cutters that are expanded laterally outward byhydraulic pressure applied through the fluid in the drill string towhich the bit is attached, and

in which the cutters are held in their expanded position by hydraulicpressure despite the relieving of the pressure in the fluid in the drillstring itself.

Another object of the invention is to provide an expansible rotary drillbit having cutters which are held hydraulically in their expandedposition despite the relievi lexpanded position, but in which thetrapped fluid can be released whenever retraction of the cutters isdesired.

Yet another object of the invention is to provide an expansible rotarydrill bit embodying a cylinder and piston device for expanding thecutters laterally outward, in which the opportunity for sand, and otherforeign substances, in the drilling fluid to plug the device and preventretraction of the cutters is greatly minimized.

lStill a further object of the invention is to provide an expansiblerotary drill bit embodying a cylinder and piston device for expandingthe cutters laterally outward, in which iluid under pressure can ybetrapped in the device to hold the cutters outwardly, and in which thebit embodies a safety mechanism for insuring retraction of the cuttersin the event that the trapped fluid in the device cannot be released inthe normal manner, or in the event the device becomes plugged with sandor other foreign substances.

This invention possesses many other advantages, and has other objectswhich may be made more clearly apparent from a consideration of a formin which it may be embodied. This form is shown in the drawingsaccompanying and forming part of the present specication. it will now bedescribed in detail, for the purpose of illustrating the generalprinciples of the invention; but it is to be understood that suchdetailed description is not to be taken in a limiting sense, since thescope of the invention is best -dened by the appended claims.

Referring to the drawings:

Figure l is a longitudinal section through an embodiment of theinvention dispo-sed in a well bore, with the cutters and other parts intheir initial and retracted positions;

Fig. 2 is a longitudinal section similar to Fig. 1, disclosing thecutters locked in their fully expanded position;

Fig. 3 is a cross-section, on an enlarged scale, taken along the line3-3 on Fig. 2;

Fig. 4 is a fragmentary longitudinal section, on an enlarged scale,through the hydraulic actuating mechanism of the device, with the partsoccupying substantially the same position as disclosed in Fig. l;

Fig. 5 is a View similar to Fig. 4, disclosing the hydraulic actuatingmechanism in the position it occupies when the cutters are expanded totheir fullest extent;

Fig. 6 is a view similar to Fig. 4, disclosing the hydraulic mechanismin a position between the locations shown in Figs. 4 and 5.

The form of invention shown in the drawings includes a rotary expansibledrill bit A which can be secured to the lower end of a string of drillpipe B extending to the top of the well bore C, and by means of whichthe drill bit is lowered through a string of Well casing D to a regionbelow the casing shoe F where the hole enlarging operation is tocommence. The general type of expansible drill bit shown in the drawingsis both illustrated and described in Patent No. 2,545,036, to whichattention is invited for certain structural details that are notdisclosed nor described herein in detail.

The upper portion of the rotary drill bit consists of a tubular mandrell@ having an upper pin l1 threadedly connected to a sub l2 formed on thelower end of the string of drill pipe B. This mandrel includes an upperkelly or drill stern member 13 slidably splined to the `rain body 14 0fthe drill bit. The exterior 15 of the lower portion of the kelly isnon-circular or hexagonal in shape, being telescopically received in acompanion noncircular or hexagonal socket 16 formed in the main bit body14. The hexagonal kelly exterior l5 and companion socket 1d form aslidable splined connection between these parts, enabling the kelly 13to be moved longitudinally with respect to the body 14, while beingcapable of transmitting rotary movement to the body.

The mandrel lil has a limited range of longitudinal movement within thebody 14, its downward movement being determined by engagement of thelower end 17 of the kelly with an inwardly directed shoulder 18, itsupward movement being limited by engagement of an external shoulder orpiston portion 19 of the kelly, fitting Within a counterbore o@ in thebody of theA tool above its hexagonal socket t6, with a lower abutmentmember 72 that rests upon a shoulder 73 formed in the body i4 0f thetool. This abutment 72 constitutes part of a packing structure carriedby the body of the tool, as described hereinbelow. Actually, theabutment 72 may be considered as constituting the upper end of aconlined cylinder space 22 formed between the kelly or drill stem 13 andthe body 14 of the tool.

The tool body 14 has a plurality of expansible parts mounted on it.These include cutter supporting members 23 pivotally mounted in bodyslots 24 on hinge pins 25 suitably secured to the body. Each cuttersupporting member 23 depends from a hinge pin 25, terminating in abearing supporting pin 2o inclined inwardly and downwardly. A sideroller cutter 27 is rotatably mounted on each bearing supporting pin 26,being mounted on antifriction roller and ball bearing elements 28, 29rollable on the bearing supporting pin. The ball bearing elements 29lock the cutters 27 against endwise movement on the bearing supportingpin 26, as well as transmitting axial and radial thrusts between thecutter and supporting pin. The roller bearing elements 28 transmitprimarily radial thrusts between these parts. The manner of mounting theVball and roller bearing elements 29, 28 between the cutters 27 andbearing supporting pins 26, and of retaining them in place, isspecifically described in the above-mentioned Patent 2,545,036.

The Ycutter supporting members 23 and cutters 27 mounted therein tend tooccupy a retracted position substantially and entirely within thecontines of the main body 14 of the bit. These cutter supporting membersand cutters are expandible outwardly, to enlarge the sides of the wellbore C and to operate upon a formation shoulder E that the cuttersproduce in the latter. To accomplish the expansion, each cuttersupporting member 23 has an inclined expander surface 30 on its innerportion 31 below the hinge pin 25 which tapers in a downward and inwarddirection. face 30 terminates in a lock surface 32 formed on a lockportion 33 of the cutter supporting member. The outward expansion isaccomplished by producing relative longitudinal movement between themandrel and the bit body 14, which will produce corresponding relativelongitudinal movement between the cutter supporting members 23 and thetubular member 34 of the mandrel. This tubular member 34 includes alower portion 35 slidable within a guide 36 secured to the body 14 andextending across the slotted region of the body below the lock portion33.

Located initially substantially above the guide 36 and below the hingepins and in cutter supporting member recesses 37 is a mandrel lock andexpander 38 having outer surfaces 39 adapted to engage the expandersurfaces and the lock surfaces 32. The lock and expander 38 may beformed integrally with the tubular member 34, the upper end of thelatter being piloted within a socket 40 in the lower portion of thekelly 13. An enlarged boss 41 on the tubular member engages a downwardlyfacing shoulder 42 of the kelly, the tubular member being held in thisshoulder by a suitable split retainer or lock ring 43 snapped into aninternal groove 44 encompassing the Kelly socket 40 and engaging adownwardly directed shoulder 45 formed on the tubular member boss 41.Leakage between the boss 41 and the wall of the Kelly socket isprevented by a suitable side seal 51, in the form of a rubber O ring,disposed within a groove 52 in the boss and engaging the wall of thesocket 40.

The kelly 13 has a central uid passage 45 therethrough communicatingwith the string of drill pipe B. Fluid pumped through this passage 46can pass into an aligned central passage 47 in the tubular member 34,whereby drilling mud, or similar drilling fluid, can be pumped downthrough the tool, for the purpose of removing the cuttings from the wellbore C and ilushing them upwardly around the drill pipe B to the top ofthe hole.

Assuming that the body 14 of the tool is elevated relatively along thetubular mandrel 10, the inclined expander surfaces 30 of the cuttersupporting members 23 will be shifted upwardly along the lock andexpander portion 38 of the tubular member. During such upward shifting,the cutter supporting members 23 and the critters 27 carried thereby maybe pivoted about the hinge pins 25 and urged in an outward direction.The movement of the body 14 with respect to the tubular mandrel 1t) cancontinue until the cutters 27 have been shifted outwardly to theirfullest extent, as determined by engagement of stop shoulders 53 on thecutter supporting members with companion shoulders 54 formed in the bodyon opposite sides of the body slots 24. When such engagement occurs, thelower end 17 of the Kelly portion of the tubular mandrel 10 will engagethe body shoulder 18, and the lock and expander 38 on the tubular member34 will be disposed behind and in engagement with the lock portion 33 onthe cutter supporting members 23.

It is to be noted that the surfaces 32 of the lock portion on the cuttersupporting members 23 and the companion surfaces 39 on the lock andexpander portion 38 of the tubular member are substantially parallel tothe axis of the drill bit, to prevent the reactive forces of theformation on the cutters 27 from moving the latter inwardly. As apractical matter, it is preferred that the coengaging lock surfaces 32,29 be inclined slightly in Each expander sur- 7 4 a downward directiontoward the axis of the tool, to insure release of the lock and expanderportion 38 from the cutter supporting members 23 when the latter and thecutters 27 are to be shifted back to their retracted positions.

The relative longitudinal movement between the tubular mandrel 10 andthe body 14 of the tool for effecting outward expansion of the cutters27 is accomplished hydraulically. The counterbore 60 receiving thepiston 19 of the drill stern member 13 is formed in the upper portieri14n of the body, which actually constitutes a cylinder having a cylinderwall 61 extending from a lower shoulder 62, defining the bottom of thecounterbore 60, to an upper head and guide 63. This latter member has adepending portion 64 inserted in the upper end of the cylinder 14a andreleasably retained therein by a split snap ring 65 carried in a groove65a in the cylinder head portion 64 and adapted to be received within agenerally V-shaped internal groove 66 in the upper portion of thecylinder wall. The head 63, with the snap ring 65 mounted in its groove,need merely be forced into the cylinder 14a and, when located oppositethe V-shaped groove 66, the snap ring will expand inherently partiallyinto the latter to releasably lock the cylinder head 63 to the cylinder14a.

The conned cylinder space 22 is formed between the piston portion 19 ofthe kelly 13, the periphery of the kelly above the piston, and thecylinder 14a. To provide this space, a suitable packing or side sealstructure 67 is disposed in a suitable piston ring groove 68 formed inthe piston, which is adapted to slidably seal against the cylinder wall61 and the cylinder 14a. Fluid is thereby prevented from passing in adownward direction between the piston 19 and the cylinder 14a.Similarly, iluid is prevented from passing in an upward direction out ofthc annular cylinder space 22 by a cylindrical packing or sealingstructure 69 secured to the cylinder 14a and slidably engaging theperiphery of the kelly 13. This structure may take any suitable form. Asshown, it consists of the lower packing supporting ring or abutment 72,that rests upon the upwardly facing body shoulder 73, and which has anupper portion 74 that can slidably engage the periphery of the kelly 13,an intermediate cam surface 75 that is spaced laterally outward from theperiphery of the kelly, and a lower surface 76 inclined in a downwardand outward direction. A non-metallic packing 77, of any suitablematerial, rests upon the lower abutment 72, its upper end engaging anupper packing ring or abutment 78 bearing against a split retainer ring79 received within an internal groove 80 in the cylinder 14a. The lowerabutment 72 and the upper split retainer ring 79 prevent longitudinalmovement of the packing structure 69 with respect to the bit bodycylinder 14a. The noirmetallic packing portion 77 of the sealingstructure 69 engages the cylinder wall 61 to prevent leakage therealong,and also slidably seals against the periphery of the drill stem portion13 of the tubular mandrel 10.

Fluid under pressure in the string of drill pipe B and within thetubular mandrel 10 can be fed into the cylilb der space 22 through oneor more side ports 81 extending through the tubular mandrel 13immediately above the piston portion 19, and establishing communicationbetween the central passage 46 through the kelly 13 and the cylinderspace 22. Such uid under pressure can be developed by restricting thearea through the passage 17 in the mandrel below the ports 81, to enablea back pressure to be built up in the Kelly portion 13 of the mandrel,which pressure will be imposed on the uicl in the cylinder space 22 andacting upon the packing structure 69, to urge the body 14 of the tool inan upward direction with respect to the tubular mandrel 10, andcorrespondingly elevate the cutter supporting members 23 and cutters 27with respect to the lock and expander portion 38 of the tubular member34, expanding the cutters 27 to their fullest extent.

As 'disclosed in the drawings, the restriction in the providing thepassaget47 through the tubular member 34 with a substantially-lesserdiameter-and area than the diameter and area of the passage 46 throughthe Kelly portion 13 of the mandrel thereabove.

In'the manner described above, the cutters 27 can be expanded to theirfullest extent merely bythe act of pumpingV the fluid under pressurethrough the drill pipe B, the Kelly passage 46, and the tubular memberpassage 47a back pressure `of fluid being built up, which passes through'the inlet port S1 and into the confined cylinder space 22, to elevatethe body i4 of the tool to its fullest extent with respect to thetubular mandrel 10. The tool can be rotated, with the cutters -27operating upon the formation shoulder E, and the cutters will remainlocked in their outwardly expanded position so long as drilling weightis being imposed upon the-drill pipe B and the drill bit A. ln the eventthe ydrill pipe and the drill bit are elevated in the well bore C, andin the absence of hydraulic pressure within the tool, the body 14 wouldtend to drop down along-the mandrel 10, allowing the cutters v27 toreturn to their retracted position. Thereafter, itwould be necessary tofirst'apply pressure to the tool to reexpand the cutters 27 beforelowering the apf-paratus yback to the position in which the cuttersengage the shoulderE.

By virtue of the present invention,the cutters 2'7 are prevented fromretracting from their maximum outwardly expanded position in thevabsenceof fluid pressure within the drillpipe B and the mandrel passages 46,47, and upon elevation of thetool A to raise its cutters above theshoulder E. To accomplish vthis purpose, fluid under pressureis trappedwithin the confined cylinder space l2 -between the cylinder body portion14a of the tool and the Kelly portion i3 of the mandrel it). lSuchtrapping vis effected by preventing the fluid under pressure thatvpasses through the inletports 81 from returning through such inletports. Thus, each inlet port is surrounded 'by a valve seat 32 engagedby a valve element 83, which may be in the form of a ball, urgedinwardly against the seat by a suitable helical compression lspring '84engaging'the ball and a spring seat 85 in the'kelly. The iluid-underpressure in the Kelly passage 46 can unseat each valve ball element 83against the force of the spring "84, passing around the ball and throughan outer `passage 86 .in the kelly into the confined cylinder vspacev22.

Because of the check or one-way valve devices 82, S3

.controlling the flow of fluid through the inlet passages 8l, fluidpassing through the inlet passages into the cylin- .der space is trappedtherein yand cannot return through the inlet passages or ports.Accordingly, in the event the fluid pressure in a string of drill pipe Band in the mandrel 1t) were relieved, fluid under pressure would stillbe present within the confined cylinder space 22, to retain the cutters27 in their outwardly expanded position.

yHowever desirable it is to prevent inadvertent retraction of thecutters 27, the latter are to be retracted when the tool is to beremoved through the well casing D to the top 'of .the well bore.Accordingly, the fluid is allowed to escape from the confined cylinderspace 22 when the `cutters are to be retracted. One or a plurality ofoutlet ports 87 (Fig. 3) maybe provided through the kelly 13, theseports establishing communication between the confined cylinder space 22and the Kelly passage 46. Each of these outlet ports 87 is controlled bya valve device, including a valve seat S8 surrounding the outlet port,and engaged by a valve element 89, that maybe in the form of a ball,urged in an outward direction into engagement with the seat by asuitable helical compression spring 9i) bearing against the ball 89 andagainst a spring seat 91 formed in the kelly.

Fluid under proper pressure in the confined cylinder space 22 can urgeeach release valve element 89 inwardposition.

and inwardly through the outlet .passage 87 intothe central passage 46through the kelly. However, fluid cannot escape from the confinedcylinder space 22 through the outlet passages 87 unless the pressure ofthe fluid in the cylinder space exceeds a predetermined maximum value,which is determined by the force of-each spring 9i? tending to hold thevalve ball 89 engaged with its seat 88. The spring 90 will insure theretention of fluid under a pressure differential in the cylinder space22, inasmuch as it will only allow fluid to bleed past the valvemember89 and through 'the outlet passages S7 until the pressure differentialin the cylinder space 22 is equal to the unit pressure necessary toovercome the force of the outlet or exhaust valve springs 90.

The spring force is selected so that a certain minimum pressure will beretained in the confined cylinder space 22. As an example, the springsv90 may exert a'force corresponding to 200 p. s. i. differential in'tllecylnderspace 22, which will be applied over the whole area of theannular space between the wall 61 of the cylinder 14a and the peripheryof the mandrel l() above the piston 19, tending to hold the cutters 27in their fully expanded If this area is ten square inches, for example,then a total of 200D lbs. hydraulic force is available to hold the body14 in its upward position along the mandrel 10, and the cutters 27 intheir outwardly expanded position.

The fluid under pressure from the cylinder will be forced out throughthe outlet ports 87 against the action of the check valve 89, 9b whenthe tool is raised in the well bore C to a position in which the cuttersupporting members 23 engage a smaller diameter bore hole above theenlarged well bore portion, or the casing shoe F. When contacting thecasing shoe, the body 14 of the tool cannot move upwardly to any furtherextent, whereupon an upward pull taken on the drill string B and themandrel it) will move the piston i9 upwardly within the body,

'i parting a greater pressure to the fluid in the cylinder space 22 andforcing it outwardly through the outlet ports 87 into the centralpassage 46 through the kelly. The fluid will be forced outwardly untilthe mandrel 10 has been elevated within the body 14 to its fullestextent, as determined by engagement of the piston 19 with the lowerabutment member 72 of the packing structure 69.

The outlet ports 87 are preferably provided through the mandrel wall,usually immediately above the piston 19 so as to insure the outwardforcing of sand, or other foreign materials, that might be contained inthe fluid within the cylinder. lf the outlet ports S7 were disposed at ahigher position within the mandrel it), then the sand might tend tosettle out of the drilling fluid within the cylinder space 22 and remainupon the piston 19 below the outlet ports, thereby preventing elevationof the mandrel 10 within the body to the extent necessary to insure fullretraction of the cutter supporting members 23 and the cutters 27.

In place of, or in addition to, the valve controlled outlet passages orports 87 described above, an upper outlet port or ports 92 can beprovided in the kelly i3, this port establishing communication betweenthe central passage 46 through the kelly and the confined cylinder space22. Each upper passage 92 is surrounded by a valve seat 93 adapted to beengaged by a valve element 94, in the form of a ball, that is forcedoutwardly against the seat by a helical compression spring engaging theball 94 and a spring seat 96 in the kelly. Essentially, each of theseupper valve members 94 functions in the same way as the lower set ofoutlet or exhaust valve devices S9. An excess of pressure in the fluidin the cylinder space 22 beyond the unit pressure corresponding -to theforce of the springs 95 will unseat the ball valve element 94 and allowthe fluid in the cylinder space 22 to pass through the outlet passages92 back into the central passage 46 through the kelly i3. This actionwill l i Y 7 voccur as a result of the relieving of the pressure in thedrill pipe B and Kelly passage 46, whereupon the excess yof pressure inthe cylinder space 22 will unseat the check valve 94 and allow escape ofsome fluid back into the central passage through the kelly. A I

In the present instance, however, it is desired to relieve all of thepressure in the cylinder space 22, to facilitate retraction of thecutters 27 and avoid potential damage or injury in the event the tool istaken apart after 1t has been retrieved from the well bore. Accordingly,the upper set of valve devices 94, 95 is .positively opened uponelevation of the mandrel 10 with respect to the body 14. Assuming thatthe apparatus has been elevated until the expanded cutter supportingmembers 23 engage the casing shoe F, then the taking of an upward strainon the mandrel 10 will shift it upwardly along the b'ody 14, the fluidunder pressure escaping through the various outlet passages 87, 92 backinto the central passage 46 through the kelly 13. After partial movementof the mandrel 10 upwardly with respect to the body 14, the upper ballvalve element 94, that extends partly into the conned cylinder space 22,will engage the tapered surface 76 of the lower abutment member 72,which will force thc balls 94 inwardly against the action of theirsprings 95 away from their companion valve seats 93, thereby allowingthe luid Linder pressure in the cylinder space 22 to pass relativelyfreely through the upper outlet passages 92 baci; into the central Kellypassage 4 6. Continued upward movement of the mandrel .0 within the bodywill cause the upper ball members to slide along the inner surface 75 ofthe abutment 72, which will hold the valves 94 in their open position.

The upper set of relief valves 94, 9:3 can be used in place of the lowerset 89, 9i), or both sets be used, as desired. ln the event that bothsets are used, then the lower set will tend to minimize the opportunityfor sand, or other foreign `substances, in the cylinder space 22 to bcpacked therein and prevent full retraction of the cutters 27 und thecutter supporting members 2?. Despite the mechanical opening of theupper valve members .94, any sand in the cylinder space 22 can still beforced out through the lower outlet passages '87 to insure fullelevation of the mandrel 19 within the body 14 to the extent in whichthe piston 19 will engage the lower end of the lower abutment 72.

A safety feature is embodied in the apparatus to enable the cutters 27to be retracted in the event the cylinder space 22 becomes packed withsand or foreign substances that plug the passages 87, 92 and therebyprevent bleeding of the fluent material in the cylinder space backthrough these outlet passages into the interior 46 of the ltelly 13. Itis to be notcd that the split ring releasably securing thc cylinder head63 to the cylinder 14a engages the tapered walls of the inner cylindergroove 66. Accordingly, the imposition of a suilicient upwardlongitudinal force on the cylinder head 63 will cause the upper taperedgroove surface to force the ring 65 inwardly out of the groove 66, andallow the head to move upwardly out of and away from the cylinder 14a.The upper side Sila of the groove 80 for the split retainer ring 79 isalso tapered in an inward and upward direction, engaging a companiontapered surface on the outer corner of the split ring 7 When this ring79 is subjected to a sufficient upward axial or longitudinal force, itwill be shifted upwardly along the tapered upper groove surface Stia andinwardly out of the groove ".v'hen this occurs, thc remainder of thepacking structure 69 can move upwardly within the body 14 of the tool.

1n the event the cylinder space 22 has been substantially completelysanded up aftcr the cutters 27 have been locked in their expandedposition, the apparatus can be elevated until the cutter supportingmembers 23 engage the casing shoe F, which will prevent further upwardmovement of the body 14 at this time. The taking of an upward pull onthe drill pipe B and the mandrel 19 will then urge the piston 19 in anupward direction, the upward force being transmitted through the sandaccumulation in the cylinder space 22 to the upper backing structure 69.When this force exceeds the force that inherently holds the upperretaining ring 79 in its groove, the ring 79 will be urged inwardlybecause of its action against the tapered surface 80a of the groove,which will release the ring 79 and cause the packing assembly 69 to moveupwardly in the body with the mandrel. This combination will moveupwardly until the upper retainer ring 79 engages the lower end of thecylinder head 63. The upward force is then transmitted to the cylinderhead 63 to force its retainer ring 65 out of the cylinder groove 66, thehead then being carried upwardly with the packing structure 69 andmandrel 10 out of the body 14 of the tool. The mandrel 10 can moveupwardly in the body 14 to the extent determined by engagement of thetubular member lock portion 38 with the cutter supporting members 23,with the lock portion 38 located disposed opposite the supporting memberrecesses 37, allowing the cutter supporting member 23 and the cutters 27to retract completely within the confines of the body 14, permitting theapparatus A to be moved within the well casing D and elevated to the topof the wel] bore.

It is, therefore, apparent that a drill bit apparatus has been providedin which the cutters 27 can be expanded hydraulically by pumping fluidthrough the drill bit, the fluid under pressure passing through theinlet passages 81 into the cylinder space 22 to elevate the drill bitbody 14, cutter supporting members 23 and cutters 27 with respect to themandrel 10, to expand the cutters laterally outward to their maximumposition, where they are locked in such maximum outward position. Theinlet passages are closed against return ow of fluid therethrough by thecheck valves 83, trapping uid under a pressure differential within thecylinder space 22, that will remain therein when the fluid pressurewithin the drill pipe B and the mandrel 10 is relieved. The pressuredifferential within the cylinder space 22 is dependent upon the force ofthe springs 90, urging the outlet valve devices 89, 94 against theirrespective seats 88, 93, to prevent bleeding of the tluid under pressureback into the interior of the Kelly passage 46. Thus, the cutters 27will remain in their outwardly expanded positions until it is desired towithdraw the tool from the well bore.

When the drill pipe B is elevated, to elevate the hit A therewith, thecutters 27 will remain in their outward expanded position until arestriction in the well bore is encountered, such as the casing shoe F.The cutter supporting members 23 will engage the casing shoe, to preventupward movement of the body 14 at this time. Continued upward movementof the mandrel 10 will then apply additional pressure to the ud in thecylinder space 22, by means of the piston 19, the increased pressure ofthe uid opening the outlet valves 89, 94, and allowing the fluid toexhaust from the confined cylinder space 22 into the Kelly passage 46,the piston 19, of course, moving upwardly in the body 14 during thistime to elevate the lock portion 38 of the mandrel to its fullest extentwith respect to the cutter supporting members 23, allowing the latterand the cutters to shift completely to their retracted positions.Assurance is had that the uid pressure in the cylinder space 22 isrelieved by virtue of the engagement of the upper set of exhaust valveelements 94 with the cam device 72 that will shift and hold them intheir open position.

In the event that any sand accumulates in the cylinder space 22, it canbe forced out through the lower outlet passages 87, or, if the cylinderspace is plugged with sand or other foreign substances to the extentpreventing their outward movement through the outlet passages 87, thenthe imposition of sutiicient upward force on the piston 19 and the sandaccumulation will release the rings 79, 65 and shift the entire packingassembly said body for expansion laterally of said body; a mandrelconnectible to a drill string and slidably splined to said body; saidmandrel having a fluid passage communicating with the drill string;coengageable expander means on said mandrel and cutter means;hydraulically operable means on said body; means for feeding fluid underpressure from said passage into said hydraulically operable means toelevate said body and cutter means with respect to said mandrel to causesaid expander means to expand said cutter means laterally outward; checkvalve means in said feeding means to allow fluid flow from said passageto said hydraulically operable means and to prevent flow of fluid in thereverse direction; and means responsive to the pressure of fluid in saidhydraulically operable means to allow fluid to escape from saidhydraulically operable means.

ll. In a rotary well drilling bit connectible to a tubular drill string:a main body; cutter means mounted on said body for expansion laterallyof said body; a mandrel connectible to a drill string and slidablysplined to said body, whereby drilling torque can be transmitted fromsaid mandrel to said body; said mandrel having a fluid passagecommunicating with the drill string; coengageable expander means on saidmandrel and cutter means; hydraulically operable means on said body;means for feeding tluid under pressure from said passage into saidhydraulically operable means to elevate said body and cutter means withrespect to said mandrel to cause said expander means to expand saidcutter means laterally outward; check valve means in said feeding meansto allow fluid flow from said passage to said hydraulically operablemeans and to prevent flow of fluid in the reverse direction; means forexhausting fluid from said hydraulically operable means to said passage;and valve means in said exhausting means to control flow of fluidtherefrom.

12. In a rotary well drilling bit connectible to a tubular drill string;a main body; cutter means mounted on said body for expansion laterallyof said body; a mandrel connectible to a drill string and slidablysplined to said body; said mandrel having a fluid passage communicatingwith the drill string; coengageable expander means on said mandrel andcutter means; hydraulically operable means on said body; means forfeeding fluid under pressure from said passage into said hydraulicallyoperable means to elevate said body and cutter means with respect tosaid mandrel to cause said expander means to expand said clltter meanslaterally outward; check valve means in said feeding means to allowfluid flow from said passage to Said hydraulically operable means and toprevent flow of fluid in the reverse direction; means for exhaustingfluid from said hydraulically operable means to said passage; valvemeans in said exhausting means to control flow of fluid therefrom; andmeans on said hydraulically operable means cngageable with saidlastmentioned valve means to shift said last-mentioned valve means toopen position.

13. in a rotary well drilling bit connectible to a tubular drill string:a main body; cutter means mounted on said body for expansion laterallyof said body; hydraulically operable means operatively connected to saidcutter means and subject to the pressure of fluid in the drill stringfor expanding said cutter means laterally outward; means for entrappingfluid under pressure in said hydraulically operable means to hold saidcutter means expanded laterally outward upon relieving pressure on thefluid in the drill string; said hydraulically operable means including ahead portion; means releasably securing said head portion to theremainder of said hydraulically operable means; said releasable meansbeing released when said head portion is subjected to a predeterminedforce within said hydraulically operable means.

l4. ln a rotary well drill bit connectible to a drill string: a mainbody; cutter means mounted on said body for expansion laterally of saidbody; a mandrel connectible to the drill string and slidably splined tosaid body; coengageable expander means on said mandrel and cutter means;hydraulically operable means on said body subject to the pressure offluid in the drill string for elevating said body and cutter means withrespect to said mandrel to cause said expander means to expand saidcutter means laterally outward; means for entrapping fluid underpressure in said hydraulically operable means to hold said cutter meansexpanded laterally outward upon relieving pressure on the fluid in thedrill string; said hydraulically operable means including a headportion; means releasably securing said head portion to the remainder ofsaid hydraulically operable means; said releasablc means being releasedwhen said head portion is subjected to a predetermined force within saidhydraulically operable means.

l5. In a rotary well drilling bit connectible to a tubular drill string:a main body; cutter means mounted on said body for expansion laterallyoutward of said body; a mandrel connectible to the drill string andslidably splined to said body, whereby drilling torque can betransmitted from said mandrel to said body; coengageable expander meanson said mandrel and cutter means; said body having a cylinder portionabove said expander means slidably and sealingly engaging said mandrel;said mandrel having a fluid passage communicating with the drill stringand cylinder portion to feed fluid under pressure into said cylinderportion to elevate said body and cutter means with respect to saidmandrel to cause said expander means to expand said cutter meanslaterally outward; and means for entrapping fluid under pressure in saidcylinder portion to hold said cutter means expanded laterally outwardupon relieving pressure on the fluid in the drill string.

16. ln a rotary well drilling bit connectible to a tubular drill string:a main body; cutter means mounted on said body for expansion laterallyoutward of said body; a mandrel connectible to the drill string andslidably splined to Said body; coengageable expander means on saidmandrel and cutter means; said body having a cylinder portion above saidexpander means slidably and sealingly engaging said mandrel; saidmandrel having a fluid passage communicating with the drill string andcylinder portion to feed fluid under pressure into said cylinder portionto elevate said body and cutter means with respect to said mandrel tocause said expander means to expand said cutter means laterally outward;means for entrapping fluid under pressure in said cylinder portion tohold said cutter means expanded laterally outward upon relievingpressure on the fluid in the drill string; said cylinder portionincluding a head; means releasably securing said head to the remainderof said cylinder portion; said releasable means being released when saidhead is subjected to a predetermined force within said cylinder portion.

l7. In a rotary well drilling bit connectible to a tubular drill string:a main body; cutter means mounted on said body for expansion laterallyoutward of said body; a mandrel connectible to a drill string andslidably splined to said body; coengageable expander means on saidmandrel and cutter means; said body having a cylinder portion above saidexpander means slidably and sealingly engaging said mandrel; saidmandrel having a central fluid passage communicating with the drillstring and lateral inlet passage communicating with said fluid passageand opening into said cylinder portion to feed fluid under pressure intosaid cylinder portion to elevate said body and cutter means with respectto said mandrel to cause said expander means to expand said cutter meanslaterally outward; a first valve controlling said inlet passage to allowfluid to flow from said central passage through said inlet passage intosaid cylinder portion and to prevent flow `of fluid through said inletpassage in the reverse direction; an outlet passage for conducting fluidfrom said cylinder portion to said central passage; and a second valvecontrolling said ,outlet passage, said second valve allowing uid to ilowfrom said cylinder portion through said outlet passage to said centralpassage and preventing ilow of iluid through said outlet passage in thereverse direction.

18. In a rotary well drilling bit connectible to a tubular drill string:a main body; cutter means mounted on said body for expansion laterallyoutward of said body; a mandrel connectible to a drill string andslidably splined to said body; coengageable expander means on saidmandrel and cutter means; said body having a cylinder portion above saidexpander means slidably and sealingly engaging said mandrel; saidmandrel having a central lluid passage communicating with the drillstring and a lateral inlet passage communicating with said iluid passageand opening into said cylinder portion to feed Huid under pressure intosaid cylinder portion to elevate said body and cutter means with respectto said mandrel to cause said expander means to expand said cutter meanslaterally outward; a rst valve controlling said inlet passage to allowuid to flow from said central passage through said inlet passage intosaid cylinder portion and to prevent flow of Huid through said inletpassage in the reverse direction; an outlet passage for conducting uidfrom said cylinder portion to said central passage; a second valvecontrolling said outlet passage, said second valve allowing uid to owfrom said cylinder portion through said outlet passage to said centralpassage and preventing flow of fluid through said outlet passage in thereverse direction; and means on said second cylinder portion engageablewith said second valve t'or shifting said second valve to open position.

19. 1n a rotary Well drilling bit connectible to a tubular drill string:a main body; cutter means mounted on said body for expansion laterallyoutward of said body;

a mandrel connectible to a drill string and slidably splined to saidbody; coengageable expander means on said mandrel and cutter means; saidbody having a cylinder portion above said expander means slidably andsealingly engaging said mandrel; said mandrel having a central fluidpassage communicating with the drill string and a lateral inlet passagecommunicating with said uid passage and opening into said cylinderportion to feed fluid under pressure into said cylinder portion toelevate said body and cutter means with respect to said mandrel to causesaid expander means to expand said cutter means laterally outward; a rstvalve controlling said inlet passage to allow uid to ow from saidcentral passage through said inlet passage into said cylinder portionand to prevent ow of fluid through said inlet passage in the reversedirection; an outlet passage for conducting iluid from said cylinderportion to said central passage; a second valve controlling said outletpassage, said second valve allowing fluid to flow from said cylinderportion through said outlet passage to said central passage andpreventing ow of fluid through said outlet passage in the reversedirection; said cylinder portion including a head; and means releasablysecuring said head to thc remainder of said cylinder portion; saidreleasable means being released when said head is subjected to apredetermined force within said cylinder portion.

References Cited in the iile of this patent UNITED STATES PATENTS

1. IN A ROTARY WELL DRILLING BIT CONNECTIBLE TO A TUBULAR DRILL STRING:A MAIN BODY; CUTTER MEANS MOUNTED ON SAID BODY FOR EXPANSION LATERALLYOF SAID BODY; HYDRAULICALLY OPERABLE MEANS OPERATIVELY CONNECTED TO SAIDCUTTER MEANS AND SUBJECT TO THE PRESSURE OF FLUID IN THE DRILL STRINGFOR EXPANDING SAID CUTTER MEANS LATERALLY OUTWARD;